Telephone system



Dec; 3, 1929. c oc 1,738,358

TELEPHONE SYSTEM Filed March 4, 1927 ONE WA) LOOP TRUNK drama- POZAAIZED 11m Thomas F Erucker' Patented Dec. 3, 1929 UNITED STATES PATENT OFFICE THOMAS IE. CROCKER, OF GI-IICAGO, ILLINOIS, ASSIGNOR 'IO RESERVE HOLDING COM- PANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application filed March 4, 1927. seri l no, 172,582.

The present invention relates to telephone systems in general, but is concerned more particularly with telephone systems containing both manual and automatic offices.

The broad general object of the invention is the provision of novel arrangements in connection with trunk lines from manual offices to automatic oliices for associating the calling devices with trunk lines over which automatic switches are to be operated to complete the connections. The invention is particularly applicable to systems in which plugs and jacks are provided to associate calling devices with trunks.

One object of the invention is the provision. of a calling device circuit in which the impulse circuit is normally open and cannot be closed unless the trunk line with which the calling device circuit is connected is idle, this arrangement being provided to avoid interference at a multiple switchboard.

It is a further object to give the operator a visual busy signal to indicate to her when the trunk line with which her calling device circuit is connected is busy.

According to a feature of the invention, a test conductor for the calling device circuit is provided having two branches, one branch being connected to a test relay, and the other branch being connected to a guarding source of potential, with means under the control of the test relay for transferring the test conductor from the test relay branch to the other in case the test relay does not encounter a guarding potential on the test conductor.

i-iccording to another feature of the arrangement, the switch control circuit is maintained open in a trunk line until the operator has turned her calling device off normal thereby guarding against the possibility of ;,-reliminary impulses when the operator plugs in either at the line jack or at the dial jack of a trunk line.

Another object of the invention is the provision of arrangements for automatically transferring the switch. control circuit to the calling device circuit when the callingdevice is turned off normal. and for transferring the circuit baclr LO a holding bridge in the trunk either when the operator removes the dialing plug from the dialing jack or when the called man responds, in case the calling device circult is left in association with the trunkline.

Another object of the invention is to provide means for placing a guarding potential on the test conductor of the dialing multiple so as to guard the trunk line against intru sion by other dialing circuits as long asthe trunk line is in use and after the dialing circuit used to set up the connection has been disassociated from the trunk line. i

It is a further object of the invention to provide an arrangement for enabling the calling subscriber to hear any tone signals encountered by theautomatic switches during the process of setting up the connection, while the calling device is associated with the trunk. A further object of the invention is to provide, in connection with a two-way simplex dialing trunk line, an arrangement whereby the simplex dialing and supervising circuit is normally open so as to permit a ringing response device to operate over the trunk line when a call comes in, and is closed when the operator plugs in to permit dialing and supervision to be carried out over the simplex circuit. i p

According to a further feature of the invention, the simplex circuit has been arranged so that the switch control circuit is trans ferred to the calling device circuit only While the calling device is actually off normal, thereby preventing any danger of preliminary im-' pulses when the calling device plug is being inserted into the dial jack. Referring now to the accompanying drawing, Fig. 1 shows a one-way t-runk line TL outgoing from'a manualboard of the multiple type to an automatic oflice in which the auto matic switches are operated over a loop circuit. The trunk circuit TC is interposed be tween theline jack LJ and the dial jack DJ and the trunk line to perform certain switch ing operations to be hereinafter explained.

To the left of the dial jack DJ there is pro- 9 vided a dial cord terminating inthe dial plug P and having certain relays and the calling device (dial) CD associated therewith. This dial cord is located at an operators position, a similar cord being provided at each of the other positions of the multiple board. The

busy lamp 101 is associated with the busy relay 102 so as to give the operator a visual busy signal in case the dial jack in which the plug P is inserted tests busy.

. In Fig. 2, the trunk line TL is shown'outgoing from a manual switchboard to an automatic ofiice in which the switches are operated "over the two conductors of the trunk line in multiple anda ground return. The line jack LJ and the dial jack DJ 2 associated with the trunk line TL are not multipled to any other positions of the switchboard. As a result, no usy testing arrangement is necessary in connection with the dial cord terminating in the plug P 5 For adisclosure of the automatic switches which .will operate in conjunction with the trunk line TL, reference may be had to the copending application of Norman H. Saunders,.Serial No. 153,791, filed December 10, 1926. Q The cord circuit used at the switch-- boards inv the present application may be of the well known common battery type, a suitable cord circuit being shown in the abovementioned Saunders application.

' Regarding theautomatic switches operated over the trunk line TL these switches may be of the well known two-wire type, the connector switches being'arranged to reverse the current flow in the trunk line when the called man responds. Such switches are shown in Patent 1,614,678.

The invention having been described generally,'a detailed description of the operation of the apparatus shown will now be given.

' For this purpose, it will be assumed that the operator at the switchboard shown in Fig. 1 tests the sleeve of the line jack LJ with the tip of her cord and finds the trunk line idle. The operator thereupon inserts the plug of her cord into the jack LJ whereupon relay 105 operatesover. the sleeve of the plug and jack inseries, preparing circuits for relays and the busy relay 102 will not operate.

Therefore, no rela operation takes place when the plug P is mserted into the dial jack.

The operator now turns the calling device CD in accordance with the. first digit in the desired number. As soon as the dial of the calling device moves 01f normal, a circuit is closed at the off-normal contacts thereof for the upperwinding of the relay 103 through the armature, normal, of relay 102. Relay 103 prepares the impulse circuit at its inner armature, and at its lower armature disconnects the test conductor (the ring conductor) of the plug P from test relay 102 and connects it to the lower winding of relay 1033, thereby placing battery on the ring of the plug and ack through the lower winding of relay 108. This closes a circuit through the upper armature, normal, of relay 106 for the marginal transfer relay 109 through the lower armature of relay 105 to ground. Relay 109 operates over this circuit and closes a looking circuit for itself at its inner upper armature independent of the upper armature of relay 106. At its upper and lower armatures, relay 109 connects the outgoing tip and ring trunk conductors to the tip and sleeve, respectively, of the dial jack DJ the connection to the sleeve conductor including the lower winding of induction coil 108 for a purpose to be pointed out hereinafter. The outgoing trunk conductors are thus connected to the prepared bridge in the dial cord including the tip and sleeve conductors of the plug P inner armature of relay 103, contacts of the release key, polarized relay 104, and the impulse springs of the calling device CD When this circuit is closed the automatic switch to which the trunk line TL extends is prepared for operation in the usual manner. Relay 104;, being correctly polarized, does not operate at this time.

In the trunk circuit TC as a further result of the operation of relay 109, a circuit is closed at its inner lower armature for the lower windings of relays 106 and 107 in multiple. Relay 106 operates at this time but the electro-polarized relay 107 does not operate. Upon operating, relay 106 closes at its lower armature a locking circuit for its lower winding through the inner armature of relay 105. At its inner upper armature, rclay 106 closes a bridge including the upper winding of relay 107 and the upper winding of induction coil 108 across the disconnected talking conductors to the right of the talking condensers so as to provide a holding circuit for the automatic switches after relay 109 falls back. At its upper armature, relay 106 opens the initial circuit of the relay 109, leaving relay 109 operated through its inner armature, and connects the test conductor to battery through the high resistance 110 so as to maintain the test contact of the dial jack DJ 1 busy as long as the plug of the calling cord circuit is in line jack LJ As the calling device CD returns to its normal position, the impulse circuit is interrupted at the impulse springs of the calling device a number of times depending upon the forward position to which the dial of the calling device was advanced. When the normal position of the calling device is again reached, the off-normal contacts of the calling device open the circuit through the upper winding of rela y 103, but 1'elay 103 remains operated When the operator again turns her calling device CD, the oil normal springs again close, but without any particular utility at this time as relay 103 is already operated. The impulsing circuit is again opened the required number or times by the impulse contacts of the calling device as thedial returns to its normal position.

After the operator has dialed the complete number, the circuits remain in the same condition until the operator removes the plug P from the jack DJ or until the called man responds. It will be assumed first for the sake of illustration that the operator has received another call before tl hrst called man has responded and that she has need of the dial cord to set up another automatic connection. 111 this case the operator pulls the plug P from the. jack Dil When the plug is removed, the bridge across the conductors of the trunk line TL is opened at the tip and sleeve contacts, and the initial circuit for relay 109 through the lower Winding oi relay 103 is opened at the ring contact of the plug and jack. A circuit for relay 100 now exists through the upper "mature, operate-d, of relay 106 and the inner upper armature of relay 109. Relay 100, however, being marginally adjusted is unable to remain operated in series with the relatively high resistance 110, and quickly falls baelz,transferring the outgoing trunk conductors to the local bridge including the inner upper armature of relay 106, upper winding of relay 10? and the upper Winding of the induction coil 108. This transfer is made by relay 109 very quickly and the establis led connection is not released. It may occur, however, thatthe line relay of the connector in use falls back momentarily, but this does not cause any further movement of the connector Wipers for reasons Well lu'iown. Current is new flowing through both windings of relay 107, but the relay is not operated owing to the direction in Which the relay is polai ized.

It wi l now be assumed that the operator does :no' eive another automatic call right away and that she accordingly leaves the plugl in the dial jack Dil Under this con dition, it the called line is busy, busy tone current flows over the trunk line conductors from the operated connector and through the dial cord. These tone currents are repeated at the induction coil 108 into the prepared holding bridge, with the result that the calling subscriber hears the busy signal. Assun'iing now that the called line isidle, the polarized relay 10 1: is operated When the reversal of current takes place When the called man responds. Upon operating, relay 104; applies ground to the ring conductor of the plug P short circuiting relay 109 in the trunk circuit- Tc Relay 109 lets go and transfers the. outgoing trunk conductors to the local bridge including the upper Winding of relay 107. At its inner upper armature, relay 109 disconnects itself from the ring conductor of the. dial jack, the upper arma ture of relay 106 being in an operated condition.

Responsive to the disconnection of the out going trunk conductors from the bridge including the polarized relay 104 of the dial cord, relay 104i falls back and removes ground from the ring conductor of the plug P whereupon relay 103 falls back and transfers the ring conductor to the test relay 102. lVhen this takes place, relay 102 operates in series with the resistance 110 in the trunk circuit TC which is connected to the ring contact of the dial jack through the upper armature of relay 106. Relay 102 opens a point in the circuit of relay 103 and closes a circuit for the busy lamp 101..

In the trunk circuit TC the electro polar iaed relay 10? operates responsive to the transfer of the holding circuit to the bridge including its upper Winding, as the current reversal has already taken place. Upon operating, relay 107 closes a bridge across the tip and ring conductors of the jack L1 including the upper Winding of relay 106. l Vhen this occurs, the supervisory relay in the common battery cord circuit operates over the tip and ring conductors of the jack LJ and extinguisher; the calling supervisory lamp. The calling and called subscribers may now converse with each other in the usu al in anner.

hen the conversation has been terminated, the two subscribers replace their receivers. lVhen the receiver is replaced at the automatic substation, the connector in use reverses the current flow in the conductors of the trunk line Tl back to normal, Whereupon the electro polarized relay 107 in the trunk circuit TC falls back and opens the bridge across the talking contacts of the jack Lil. l-Vhen this occurs the supervisory relay in the cord circuit falls back and permits the associated supervisory lamp to light as a disconnect signal.

When the operator removes the plug from too jack LJ relay 105 falls back and opens the locking circuit of relay 106 and the circuit of the lower Winding of relay 107. Relay 106 falls back and opens the holding bridge at its inner upper armature and removes the guarding potential from the ring contacts of the dial. jack DJ The automatic switches release as a result of the opening of the holding bridge.

In the dial cord, the busy relay 102 falls back When the guarding potential is removed from the ring conductor by relay 106. The lamp 101 thereupon becomes extinguished.

.Incase the operator receives another call to be completed over the trunk line TL before .this trunk line istaken for use by another operator at one of the multiples of the line jack LP, the operator may plug in the line jack LJ and start dialing her number right away without performing any busy test as the unlighted condition of the lamp 101 indicates to her that the trunk line is idle.

- and preventing the operation of the transfer relay corresponding to relay 103. For this reason, ifv tyvo operators start to turn their dials at about the same time the unsuccessful operator will note that her busy lamp cor- 4 responding to lamp 101 becomes lighted and she will cease to dial and take another trunk.

- It; will be notedthat the loop is not closed in the dial cord of the unsuccessful operator because relay 103 of the unsuccessful cord is prevented from operating.

In order to handle the traffic efficiently at night, the operators are withdrawn from dutyas the traffic becomes lighter and lighter, and there is in many installations only one operator on duty during several hours at night. At such times, there may be 00- casional rises in traffic until the calls come in faster than one operator can conveniently handle them, but this usually lasts for only a few minutes with the result that the night operator can eventually dispose of all the waiting calls. During such busy periods, the night operator is able to take a short cut, so to speak, in handling a connection which con- 7 dial jack, such as the dial jack DJ permissible for her to do this during the night sists in starting to turn the dial of the calling device CD at the same time that she takes a hold of the plug P, Fig. 1, to insert it into a It is since no other operator is working and the busy-test arrangements in the dial cord are, therefore, of no utility at this time.

"With the calling device CD off-normal at the time the plug P is inserted into a jack (the jack DJ for example), relay 103 is operated and a battery potential through the lower winding thereof appears onthe ring conductor of the plug P operating relay 109 assoon as the plug is fully inserted into the jack. Under this condition, it is particularly advantageous to employ the ring conductor instead of the sleeve conductor for the energiza tionof relay 109, because the ring contact of the plug is the last contact of the plug to close with the corresponding contact of the jack, and it does this just before the plug is fully inserted and after the other two contacts of the plug are in engagement with the correspondin contacts of the jack. If the conductors o the plug P and the jack DJ 1 were connected up in the normal way with the testing operation and the operation of relay 109 carried on over the sleeve conductor, there would be the danger of preliminary impulses upon the insertion of the plug P into ack DJ especially in the case of worn plugs or jacks, on account of the likelihood of relay 109 dropping back one or more times after it is pulled up following a partial or hesitant insertion of the plug into the jack. In addition to the likelihood of causing preliminary impulses, objcctional clicking in the talking circuit extending back to the calling subscriber is caused by the chattering action of relay 109 in case such action occurs. \Vith the arrangement as shown, however, there is no chattering action of relay 109 as this relay does not operate until the plug is practically fully seated in the ack.

Referring now to Fig. 2, the arrangement shown therein will be described. For this purpose it will be assumed first that a call is received over the trunk line TL from the automatic office. When the connection is completed to the trunk line TL in the automatic ollice, ringing current is projected over the two conductors thereof, operating relay 200, whose upper winding is bridged around the condenser between the two right-hand repeating-coil windings. Relay 206 closes a locking circuit for its lower winding at its inner armature, and at its lower armature closes a. circuit for the lamp 201.

When the operator notes the lighted condition of the lamp 201, she inserts an answering plug into the line jack LJ hen the plug is fully inserted, a circuit is closed over the tip and ring contacts of the jack and through the left-hand repeating-coil windings for relay 203. Relay 203 operates and places ground on the lower terminal of sleeve relay 202. Relay 202 operates and closes a locking circuit for itself independent of relay 203, at the same time opening the locking circuit of relay 206. Relay 206 now falls back and the lamp 201 becomes extinguished. At its upper armature relay 202 shunts the condenser associated with the right-hand repeating-coil windings, and at its inner upper armature it places ground on the upper terminal of supervisory relay 205, thereby applying a ground potential through inner contacts of relay 204 to both conductors of the trunk line TL? This application of ground potential results in the removal of the source ofiringing current in the manner explained in the Saunders application hereinbefore referred to. Relay 205, however, does not become operated at this time. As a result the operator receives dark supervision in the answering end of her cord circuit.

The operator now completes the connection to the desired subscriber in the usual manner.

When the conversation is over the two subscribers replace their receivers. When the automatic subscriber replaces his receiver, the automatic switches release and the supervisory relay 205 becomes operated owing to the placing of an operating potential on the two conductors of the trunk line TL in the automatic exchange as disclosed in the abovementioned Saunders application. When relay 205 operates it opens the bridge across the tip and ring contacts of the jack LJ whereupon relay 203 in the trunk circuit T0 and the answering supervisory relay in the cord circuit fall back. The operator is thereby given a disconnect signal and she pulls down the connection. When the; connection is pulled down, relay 202 falls back and opens the circuit of relay 205 whereupon relay 205 restores.

Assuming now that the operator" receives a call for a connection to be set up over the trunk line TL she inserts the calling plug oi a cord circuit into the line jack LJ whereupon relay 203 operates as before and connects up the sleeve relay 202. Relay 202 operates as before, closing a locking circuit for itself at its lower armature, shorting the right-hand condenser associated with the repeating coil windings, and placing ground on the upper terminal of relay 205. As the conductors of the trunk line TL norm ally extend to battery in the automatic exchange, relay 205 operates over the two conductors of the trunk line TL in parallel and opens the bridge across the tip and ring conductors of the line jack LJ so as to cause the supervisory lamp in the operators cord to become lighted. The closure of the circuit over the trunk line including relay 205 results in the preparation of the apparatus in the automatic oflice to respond to the impulses.

The operator now inserts the plug P into the dial jack DJ It will be noted that no relay operation takes place as a result of the mere insertion of the plug into the jack, thereby avoiding any possibility of preliminary impulses due to careless or hesitant insertion of the plug P into the jack.

When the operator turns the calling device ofl normal, a circuit is closed over the tip of the plug and jack for the transfer relay 204. Relay 20 loperates and disconnects the simple dialing conductor from relay 205 and transfers it to ground through the ring conductor of the jack and plug and the impulse springs of the calling device CD Relay 2041: 150 opens a point in the bridge across the tip and ring contacts of the line jack LJ so as to prevent this bridge from becoming closed when relay 205 falls back responsive to being disconnected by relay 204.

The impulses are transmitted by the impulse springs of the calling device CD as the dial thereof returns to its normal position. When the normal position is reached, re-

ay 204i again falls back and relay 205, being reconnected, again operates.

The operator, after having dialed the complete number, may leave the plug P in the jack DJ or remove it as she sees fit.

"When the called subscriber res onds, the current flow over the conductors o the trunk line TL is reduced in the manner explained in the above-mentioned Saunders applica tion. hen this takes place, the marginal supervisory relay 205 falls back and completes the bridge across the tip and ring conductors of the jack LJ whereupon the supervisory relay in the calling end of the cord circuit responds and extinguishes the associated supervisory lamp to giveanswered supervision. The two subscribers may now converse with each other.

When the called subscriber replaces his rcceiver upon the termination of the conversation, the current flow over the conductors of the trunk line TL is restored to its normal value, whereupon relay 205 reoperates, resulting in the relighting of the supervisory lamp of the operators cord circuit as a disconnect signal.

When the operator pulls down the connection upon perceiving the disconnect signal above mentioned, relays 202 and 203 fall backand relay 202 disconnects ground from the upper terminal of relay 205 whereupon relay 205 falls back also and the switches in the automatic ofiice release responsive to the cessation of current flow over the conductors of the trunk line TL What is claimed is:

i. In a telephone system in which automatic switches are operated from a manual switchboard to set up telephone connections, a trunk line outgoing from the manual switchboard to the automatic switchboard, a switch operating circuit including the conductors of said trunk line, means in said circuit for controlling the automatic switches to extend the connection, and means controlled over said circuit for initially closing a holdin circuit for the automatic switches responsive to the response of the called subscriber and for opening said operating circuit.

2. In a telephone system, a trunk line divided into two sections and extending from a manual switchboard to an automatic switchboard, a switch operating circuit, means for dividing the trunk line into its two sections and for connecting said switch operating circuit to the second section, means for preparing a switch holding circuit including the two sections of said trunk line in series, and

means forfautomatically disconnecting said operatingcircuit from the second section and -fr uniting the two sections of the trunk line when acalled subscriber responds to a con- 1; -nection set up under the control of said switch operating circuit. r

"3. In a telephone system, a trunk line extending from a manual switchboard to an automatic switchboard, a calling device at 1 1o said manualwswitchboard, a normally open switch operating circuit including said cell ing device and said trunk line, a normally open switch holding circuit including said trunk line and excluding said calling device, 1 and means responsive to the movement of said calling device off normal for completing said switchoperating circuit and for preparing saidswitch holding circuit.

4.;In a telephone system, a trunk line 6X "gof'tending from a manual switchboard to an automatic switchboard, a calling device at 'saidmanual switchboard, a normally open switch operating circuit including said calling device and said trunk line, a normally open'switch holding circuit including said trunk' line and excluding said calling device,-

ineans'r'e sponsive to the movement of said calling device ofl' normal for completing said "switch'oper'ating circuit and for preparing said switch holding circuit, and locking means for maintaining the said circuits closed and prepared, respectively, after the calling device has returned to its normal posi- ''tion. I I

5. In a telephone system, a plurality of trunk lines extending from a manual switchboard to an automatic switchboard, a pluralityof'calling devices at said manual switchboardj for controlling automatic switches at "the'ai1toma-tic switchboard over said trunk lines, means for connecting any one of said calling devices to any desired trunk line, and means for preventing a second calling device from being; connected to any trunk line.

6, In a telephone system, a trunk line extending from a manual switchboard to an automatic switchboard, a calling device at the manual switchboard for controlling the auto matic switches at the automatic switchboard,

operator-controlled means for associating said calling device with said trunk line, a switch-control circuit including said trunk line, and means responsive to the oil-normal movement of said calling device for connecting the calling device with the trunk line, and

for initially closing said switch-control circuit,'the switch-control circuit at this time including said calling device.

'7. Ina telephone system, a trunk line extending from a manual switchboard to an automatic switchboard, a calling device at the -manual switchboard for controlling the switches at the automatic switchboard, means for associating said calling device with said trunk line, a relay individual to said calling device for connecting the same with said trunk line when the calling device is moved oif normal, and a holding circuit for said relay including a conductor individual to said trunk line.

8. In a telephone system, a trunk line extending from a manual switchboard to an automatic switchboard, a calling device at the manual switchboard having impulse contacts for controlling the switches at the automatic switchboard, means for associating the impulse contacts of said calling device with said trunk line, and means individual to said trunk line for connecting the calling device with said trunk line when the calling device is moved ofi normal.

9. In a telephone system, a trunk line eX- tending from a manual switchboard to an automatic switchboard, a calling device at the manual switchboard for controlling the switches at the automatic switchboard, means for associating said calling device with said trunk line, and means including a connecting device individual to the calling device and another connecting device individual to the trunk line for connecting the calling device with the trunk line responsive to the calling device being moved from its normal position.

10. In a telephone system, a multi-position manual switchboard, a trunk line multipled into several positions of said switchboard and extending to an automatic switchboard, a calling device at each of said positions associated with said trunk line, means for connecting any one of said calling devices with said trunk line, and means for preventing any calling device from belng connected with said trunk line in case another calling device has already been connected therewith.

11. In a telephone system in which automatic switchcs are controlled by calling devices at a manual switchboard, a calling device having a test conductor and an operating conductor associated therewith, a normally open point in said operating conductor, and a relay controlled over said test conductor for preventing a closure of said normally open point.

' 12. In a telephone system in which automatic switches are operated by calling devices located at a manual switchboard, a calling device at a manual switchboard having associatedtherewith an operatingconductor and a test conductor, a normally open point in said operating conductor, means for closing said normally open point responsive to an off normal movement of said calling device,

and means for maintaining said operating circuit open in case a busy potential is on said test conductor, said means including a relay operated over said test conductor responsive to a busy potential thereon.

13. In a telephone system, a trunk line extending from a manua switchboard of the multiple position type to an automatic switchboard, said trunk line being multipled into a plurality of positions, a line jack and a dial jack for said trunk line at each of said positions, guarding means at said trunk line for placing a guarding potential on each of said dial jacks, said busying means being nonresponsive to an insertion of a plug into a line jack and nonresponsive to the insertion of a calling device plug into the dial ack, and means associated with a calling device whose plug has been inserted into a dial jack for placing a guarding potential on the test contact of said jack, said guarding means at the trunk line being rendered effective tor maintaining a guarding potential on said test con tact until the plug has been removed from the line jack of the trunk line.

14:. In a telephone system in which auto matic switches are controlled by calling devices at manual switchboards, a signal individual to each calling device, a trunk line, two calling devices associated therewith, means for connecting one associated calling device with said trunk line, and means responsive thereto for operating the signal at the other associated calling device.

15. In a telephone system, in which a plurality of trunk lines extend from a multiposition manual switchboard in one exchange to an automatic switchboard in another exchange and in which each trunk line terminates at each position of the manual switchboard in a talking jack and in a dial jack, a plug-ending dial cord at each position including a dial-type calling device, a separate switch-control circuit for each trunk line including a talking conductor of the trunk line, and circuit arrangements whereby any calling device at any position may be inserted into the switch-control circuit of any trunk line through the associated plug and the auxiliary jack of such trunk line.

16. In a combined manual and automatic telephone system, a multi-position manual switchboard, a trunk line at one position of said board outgoing from a talking jack to an automatic switchboard at another exchange, an auxiliary dial jack at said position, a calling device at said position, means including a plug individual to said calling device for connecting said calling device with said dial jack, means for transferring the talking conductors of said trunk line from said talking jack to said dial jack, and separate multiple connections from each of said jacks to similar jacks at each of the other positions of said switchboard.

17. In a combined manual and automatic telephone system in which automatic switches are controlled over trunk lines extending from a manual switchboard and in which talking connections are made to a trunk line through the medium of a line ack and separate switch-control connections are made to such trunk line through the medium of a dial jack auxiliary to the line jack, each jack having tip, ring, and sleeve contacts, the talking connections to the line jack being such that the talking conductors appear on the tip and ring contacts thereof, and connections be- 18. In a combined manual and automatic telephone system in which trunk lines outgoing trom manual switchboard to an automatic switchboard are each represented by a calling device jack, tip, ring, and sleeve contacts for each jack, a calling-device cord ending in a plug having cor1.'e.= -:ponding contacts, and means including the sleeve of the plug and jack together with another contact of the plug and jack for completing a connection from the talking conductors of the trunk line to the calling device in the cord.

19. In a combined automatic and manual telephone system in which the automatic switches are controlled by the operator through the medium oi. a calling device included in a dial cord ending in a plug having tip, ring, and sleeve contacts and in which auxiliary jacks are provided, one for each trunk line, having contacts corresponding to the said contacts oi the plug, and a switchcontrol bridge across the talking conductors of a connected trunk line including said calling device and the tip and sleeve contacts of said plug and the auxiliary jack of the trunk line.

20. In a combined automatic and manual telephone system in which a switch-controlling calling device is arranged to be asso ciated with trunk lines, over which automatic switches are to be controlled, by means of a plug associated with the calling device and a jack associated with each trunk line, a switch-control circuit formed by the two talking conductors of any trunk line and the impulse springs of said calling device, said circuit including the tip and sleeve contacts of the plug and any ack into which it is inserted, and a test circuit including the ring contact of said plug and the corresponding contact of any cooperating jack.

21. In a combined manual and automatic telephone system in which automatic switches are controlled over a trunk line extending thereto from a manual switchboard, a calling device at said manual switchboard, means for associating said calling device with a particular one of said trunk lines while maintaining the outgoing conductors thereof in their normal condition, means responsive to an off-normal movement of the asociated calling device for closing a switch-control circuit over said trunk line, means also responsive to the oil-nonnal movei'i'ient of said calling device for preparing a switch-holdin g board, said'control being eiiected by interrupting a flow of direct current over a trunk line, there being no 'switclrcontrol current flow over said trunk line normally, a calling deviceand means for associating it with any one of said trunk lines while maintaining the normal condition of such trunk line as to current fiow,,and means responsive to an offnormal movement of said calling device for setting up the said current flow in the associated trunk line.

23. In a combined manual and automatic telephone system in which trunk lines extend from a manual switchboard in one exchange to an automatic switchboard in another exchange and in which the switching mechanism in the automatic switch is prepared for operation by the setting up of a current flow over a trunk line, a calling device at said manual switchboard for interrupting the current flow to operate the automatic switches, means for associating sald calling devlce w1th a partlcular one of said trunk lines while maintaining the state of no current flow in said trunk line, and means responsive to the off-normal movement of said calling device for setting up a current flow over the associated trunk line in order to prepare the switching mechanism at the automatic switchboard for operation.

24:. In a combined manual and automatic. telephone system in which trunk lines extend from a manual switchboard in one exchange to an automatic switchboard at the other-exchange, and in which the automatic switching mechanism at said automatic switchboard is prepared for operation responsive to the establishment of a current flow over one of said trunk lines, a calling device at said manual switchboard, means for associating said calling device with one of said trunk lines, and means responsive to the off normal movement of said calling device for preparing said switching mechanism for operation by setting up a current flow over the associated trunk line.

25. In a combined automatic and manual telephone system in which trunk lines extend from a manual multi-position switchboard in one exchange to an automatic switchboard in another exchange, a calling device at each position of said manual switchboard for controlling the switching mechanism in said automatic switchboard over any one of said trunk lines, a line jack and an auxiliary calling-device jack for each trunk line at each position, a plug-ending dial cord at each position including the said calling device of such position, a signal at each calling device, and means responsive to the off-normal movement of any calling device when its associated plug is in the calling device jack of a trunk line for operating the signal associated with any other calling device which happens to be associated through the medium oi its plug with the same trunk line at another position.

26. In a combined automatic and manual telephone system in which trunk lines extend from a manual switchboard in one exchange to an automatic switchboard in another exchange, a calling device at each position of said manual switchboard, a signal individual to each calling device, means whereby the operator at any position can associate said call ing device with any one of said trunk lines, and means responsive to the off-normal movement of a calling device for operating the signal at any other ca lling device which happens to be associated with the same trunk lines at another position.

27. In a multi-oltice combined manual and automatic telephone system in which trunk lines extend from a multi-position manual 7 switchboard in one exchange to an automatic switchboard in another exchange, a calling device at each position of said switchboard, means controlled by the operator at any position for associating her calling device with any one of said trunk lines, means responsive to the off-normal movement of a calling de vice for connecting such calling device to the trunk line with which it has been associated and means effective in case another calling device has been so connected previously for preventing the said connecting means from operating.

28. In a multi-ofiice combined manual and automatic telephone system in which trunk lines extend from a multi-position manual switchboard in one exchange to an automatic switchboard in another exchange, a calling device at each position of said switchboard, means controlled by the operator at any position for associating her calling device with any one of said trunk lines, means responsive to the ofiinormal of a calling device for con necting such calling device to the trunk line with which it has been associated, means ell'ec- 'tive in case another calling device has been line and means for operating it to connect the calling device to the line, and means in the cord for shunting said relay to effect a dis connection of the calling device from the line. 30. In a telephone system in which automatic switches are controlled by calling devices at a manual switchboard, a calling device, a line over which said calling device is arranged to control the automatic switches, means including a cord circuit for associating the calling device with the line, a relay in the line and means for operating it to connect the calling device to the line, and a relay in the cord and means for operating it over the connected line to shunt the first named relay to effect a disconnection of the calling device from the line.

31. In a telephone system in which automatic switches are controlled by calling do vices at a manual switchboard, a calling device and a relay associated therewith, a line over which the calling device is arranged to control the switches, a relay associated with the line, and a circuit arrangement for operating both relays to connect said calling de' vice with the line through contacts of both relays in series.

32. In a telephone system in which automatic switches are controlled by calling deao vices at a manual switchboard, a calling de vice and a relay associated therewith, a line over which the calling device is arranged to control the switches, a relay associated with the line, and a circuit arrangement responsive to an operation of said calling device for operating bot-h relays to connect said calling device with the line through contacts of both relays in series.

33. In a telephone system in which automatic switches are controlled by calling clevices at a manual switchboard, a calling device and a relay associated therewith, a line over which the calling device is arranged to control the switches, a relay associated with I the line, a circuit arrangement responsive to an operation of said calling device for operating both relays to connect said calling device with the line through contacts of both relays in series, and means including a polarized relay associated with said calling device for shunting the relay associated with the line to disconnect the calling device.

34. In a combined automatic and manual telephone system, a cord circuit having a calling device associated therewith for controlling automatic switching apparatus, a test relay in said cord circuit, cit-normal contacts on said calling device, and circuit connections controlled by said contacts when the calling device is operated for disconnecting said test relay.

35. In a combined automatic and manual telephone system, a cord circuit having a calling device associated therewith for controL ling automatic switching apparatus, a test relay in said cord circuit, off-normal contacts on said calling device, and circuit connections controlled by said contacts when the calling device is operated for disconnecting said test relay and for substituting a guarding potential.

36. In a telephone system, a trunk line extending from a multi-position manual switchboard to an automatic switchboard, a line jack and a dial jack for said trunk line at each of a plurality of positions of said switchboard, a dial cord at each position arranged to be associated with said trunk line through a dial jack, a test relay in each cord, and means for controlling the test relay in any dial cord through a dial jack after a connection has been set up over a trunk line.

In witness whereof, I hereunto subscribe my name this 1st day of March, A. D. 1927.

THOMAS F. CROCKER. 

